Processes for refining hydrocarbon oils by means of halogen compounds



Patented Dec. 20, 1938 UNITED STATES PATENT OFFICE 2,141,143 nocnssns ron name mnooannox OILS BY MEANS POUNDS OF HALOGEN COM No Drawing. Application October 25,1937, Serial No. 170,964

8 Claims.

This invention relates to the refining of hydrocarbon mineral oils, such as petroleum oils, and oils made from coal tar and bituminous coal tar,

- to improve their qualities for lubrication, motor 6 fuel, solvents and other uses, and is a'continuation in part of our application Serial No. 12,528, filed March 22, 1935, for Processes for refining hydrocarbon oils by means of halogen compounds.

For the refining of mineral oils, selective solvents, mixturesof selective solvents or mixtures of a selective solvent with a non-selective solvent are already known. These solvents separate the main groups of hydrocarbons by dissolving for example the aromatic and unsaturated components and leaving undissolved the saturated or parafline-like groups. Some selective solvents remove also the naphthenes together with the aromatics and unsaturates.

Thehydrocarbon compounds belonging to the groups of aromatic and unsaturates and--to a certain degree also those of the naphthene groupsare well known as non-resistant against oxidation. They are further characterized by a low A. P. I. gravity, low flash and fire point, by high carbon residue and-by an unfavorable viscosity-temperature relationship. The removal of the mentioned classes of hydrocarbons results therefore in a greatly improved refined oil which the best, mineral oils known, such as fractions from Pennsylvania crude. Whereas fractions made from Pennsylvania crudes have a satisfacr tory viscosity temperature characteristic, they show nevertheless high Conradson carbon figures and require consequently expensive refining to yield a finished oil which satisfies modern demand for use in internal combustion engines.

Our invention teaches the use of a selective solvent which produces finished oils of a quality superior to Pennsylvania oils insofar as the viscosity temperature relationship of stocks of any origin is improved to that or above that of Pennsylvania oils and also insofar as the carbon residues are much lower.. The extraction by means of our solvent further greatly facilitates the finishing procedure inasmuch as the solvent extraction removes all or most of the color bearing compounds 'with the extracted fraction.

For reasons of simplicity we will refer in the following to the refined oil as rafilnate and to the undesirable or extracted fraction ,as extract.

An object of this invention is to refine hydrocarbon oils by means of a selective solvent in order to produce stable rafflnates which, when is equal to or in some instances even better, than properly finished, will fulfill the most severe specifications adopted by science for the specific products in question.

Our selective solvent is adaptable to the refining of n'aphthas in which case a saturated fraction or rafllnate is produced such as is frequently used as special solvent, for example Stoddards solvent; and the dissolved fraction or extract contains the aromatic and unsaturated components which have great value on account of their high octane number. These extracts may either be used as motor fuel directly or as a blending material for upgrading other gasolines of less satisfactory specifications.

Likewise our solvent is suitable for refining kerosenes, gasoils, transformer oils, turbine oils, the various grades of lubricating oil distillates and of residual stocks.

Depending upon the stocks to be refined and depending upon the raiilnate quality desired, the solvent may be used either alone or in combination with auxiliary solvents. These auxiliary solvents have to fulfill three different objects, namely, that of (1) increasing or (2) decreasing the solvent power or that of (3) improving the 25 selectivity of our selective solvent.

The representatives of class lof auxiliary solvents which increase the solvent power are characterized by dissolving hydrocarbon oils entirely and at the same time by being miscible with the selective solvent in each proportion. Examples of this class of auxiliary solvents are the arematics (such as benzol, tolucl, xylol, etc.), hydroaromatics, such as cyclohexane, the non-sele'ctive aliphatic and aromatic halogen derivatives, the non-selective ketones, esters, ethers and others.

Representatives of class 2 of auxiliary solvents which decrease the solvent power of our selective solvent, as identified by being miscible with our 49 selective solvent to a certain degree or in any proportion and by not dissolving'hydrocarbon oils at all or only to a certain extent. For example, water and alcohols belong to this class of auxiliary solvents, 45

The members of class 3 of auxiliary solvents which improve the selectivity of our selective solvent, are characterized by dissolving the hydrocarbon oils entirely but they are not miscible in each proportion with the selective solvent. This third class of auxiliary solvents will dissolve the hydrocarbon oils to be treated and, upon adding our selective solvent, will remain mostly in the rafilnate phase, whereas the first and second groups of auxiliary solvents (namely those which are miscible with our selective solvent) will go mainly into the extract phase. Representatives of the third class of auxiliary solvents are, for example, low boiling parafline hydrocarbons such as propane, butane, etc., or mixtures thereof.

A further object of our invention is to remove wax either from the untreated stocks to be refined or from the rafiinates, in case that wax-containing stocks are being processed. Our solvent, when blended with a suitable percentage of representatives of class 1 or class 3 of auxiliary solvents mentioned above, constitutes a very good blend for dewaxing inasmuch as these blends dissolve at reduced temperatures only the liquid hydrocarbons but leave undissolved the solid paraffine-like constituents. The removal of the solid parafline-like constituents, generally termed wax, may be efiected either by cold settling, filtration or centrifuging. The procedure becomes especially advantageous if the extraction step is combined with the dewaxing step in any desired order. For example, if the extraction is carried out first, our selective solvent may be used either alone or in combination with one or more representatives of the three classes of auxiliary solvents mentioned above, the raffinate solution, that is the undissolved layer, being saturated with the solvent used for extraction is' not charged to the solvent recovery system but is immediately dissolved in an additional amount of a blend of the selective solvent with one or more auxiliary solvents of class 1 or class 3. The quantities of selective solvent and auxiliary solvent or solvents have to be selected in such manner that separation into liquid phases will not take place at the temperature at which the dewaxing is carried out.

We have found that tetrabromoethane possesses an especially good selectivity and at the same time excellent solvent power, and this solvent is therefore especially adapted for refining of hydrocarbon oils. A further advantage of this solvent, as compared with other known selective solvents, is given by its unusually high specific gravity, which results in a much larger difference of gravity between the two layers and consequently the separation of rafiinate and extract layer is greatly facilitated. The use of centrifuges for this purpose, necessary for many other known solvents, is therefore eliminated and moreover the settling time is much less than with the other known solvents.

For carrying out our invention, for example in case of treating a waxy stock, we charge the stock to be treated to a countercurrent refining system (comprising three or more mixing and settling stages), and introduce tetrabromoethone at the opposite end of the unit. In this operation the undesirable fractions of the stock are dissolved by the counter current washing action and the rafiinate is left in undissolved form containing a certain percentage of the solvent. The solvent quantities which we use and the treating temperatures depend upon the nature of the stock and upon the quality of the rafiinate desired. Normally we employ from to of the solvent. The extract layer is charged to the solvent recovery system. The rafflnate layer is dissolved in a blend of the same solvent that was employed for the xtraction, with a mixture of equal volumes of benzol and toluol or with one or more auxiliary solvents of the above classes 1 and 3. The composition of the solvent blend, containing the selective solvent plus the auxiliary solvent or solvents, is selected in such a manner that separation into two liquid phases does not occur at reduced temperatures. We employ from 50 up to 300% of solvent blend. The dissolved rafiinate layer is cooled to about 10 F. upon which the wax separates out. The removal of the wax may be efiected by cold settling, filtration or by centrifuging.

The filtered solution is charged to the solvent recovery system of the dewaxing part of the combined unit in which the solvents are regenerated for furtheruse. From the solvent blend, recovered in the dewaxing unit, we segregate the selective solvent employed in the extraction part of the plant and recycle it to the extraction plant so as to make up the solvent that was carried over to the dewaxing plant with the waxy raffinate solution. The refined and dewaxed oil is treated with a small amount of clay either by contacting or percolating. The finished oil is of extremely good quality as shown by high A. P. I. gravity, high viscosity index, high resistance against oxidation, low carbon residue, low pour point and good and stable color.

The raw or slack wax is further processed for production of pure petrolatum. For this object we wash the wax cakes with additional quantities of solvent blend or re-extract the slack wax with a suitable composition of the same solvent mixture. By this re-extraction we remove the impurities, that is the liquid hydrocarbons, from the wax.

If deemed advantageous, we may use our selective solvent in combination with an auxiliary solvent either to increase or to decrease the solvent power or to improve the selectivity as described above.

The solvent blend of our selective solvent with representatives of the auxiliary solvents belonging to classes 1 or 3, as mentioned above, may also be used for dewaxing alone independent from the extraction process.

Instead of recovering the solvents from the hydrocarbon groups by distillation we sometimes efiect this separation by washing with a diiferent solvent in which our selective solvent is soluble but not the hydrocarbons.

' As specific examples for further demonstration of our invention, we cite the following.

Example 1 Untreated Finished stock raflinate Rafllnate yield, percent by volume 100 73 A. P. I 23. 2 28.8 Viscosity at 100 1287 065 Viscosity at 210. 91 73. 0 Viscosity index 76 99 You F 0 +10 Carbon residue 1. 9 0. 20 Color N. P. A l Dark. 5%

Eaample 2 100 volumes of a Mid-Continent residual oil are agitated with 150 volumes of s-tetrabromoethane at F. After separation of the two layers, the extract solution is removed and the undissolved portion is treated again with 50 volumes s-tetrabromoethane at '80" F. Again the solvent is recovered from the products by distillation under vacuum, and the raflinate is contacted with'clay. The degree of improvement obtained may be seen from the following table:

g fgg Railinate Raiiinate yield, percent by volume 100 34 A.P.I 20.0 27.1 Viscosity at 130. 997 440 Viscosity at 210.. 145 93 Viscosity index 78 95 Carbon residue 5. 6 l. 22

Example 3 volumes of the same stock as used in Ex ample 2 are dissolved in 100 volumes heptane and the mixture is extracted with plus '75 volumes s-tetrabromoethane at 40 F. in two steps in the same manner as above. The raflinate is then contacted with clay. The presence of heptane raised the yield considerably as shown by the followingspeciflcations of the refined oil:

Raflinate yield, per cent by volume 74 A. P. I 24.9 Viscosity at 520 Viscosity at 210 101 Viscosity in 93 Carbon residue 2.3

Example 4 One volume of a Persian, wax-free mineral oil distillate was extracted respectively at +5 1!. with an equal volume of (a) Sym. tetrabromoethane (b) Tetrabromoethane-benzol blend, containing 15 vol. percent benzol.

(c) Tetrabromoethane-methanol blend, containing 10 vol. per cent methanol.

The effect, in solvent extraction, of benzol and methanol as representatives of classes (1) and (2) of our auxiliary solvents respectively will be seen from the following table:

Rafll- Ram- Rafll iiiiiif 3 3,3 g

Yield volume, percent 100 67 61 88 A. P.I 17.5 23.1 24.3 23.0 Saybolt viscosity at 210 F... 121 88. 4 84. 2 88. 4 Viscosity index 47 80 87 79 comprising mixing the oil product with tetrabromoethane at a temperature at which part of the oil only is dissolved, separating out the undissolved part of the oil solution, and recovering the solvent from the oil solution.

2. A method of refining a mineral oil comprising extracting the oil with tetrabromoethane as a selective solvent to produce a separation into two liquid phases containing respectively parafflnic and non-parafllnic constituents, separating the phases from each other and recovering the solvent therefrom.

3. A method of refining a mineral oil comprising mixing the oil with tetrabromoethane as' selective solvent and adjusting the temperature to produce a separation into two oil containing phases, separating the phases from each other and recovering the solvent therefrom.

4. A method of refining a mineral oil compris ingextracting the oil with tetrabromoethane as a selective solvent in admixture with an auxiliary solvent to 'produce a separation into two liquid phases containing relatively paraflinic and non-parafllnic constituents, separating the phases from each other and recovering the solvents therefrom.

5. A method of dewaxing a'mineral oil com'- prising dissolving the oil in a mixture containing tetrabromoethane 'as a. selective solvent and an auxiliary solvent of the class of benzol and its homologues, said solvents being used in such proportions as not to produce a separation into two liquid layers at the dewaxing temperature, cool-. ing the oil-solvent mixture to below the desired pour point whereby the wax precipitates out, removing the wax from the oil-solvent solution and recovering the solvents from the dewaxed oil solution and from the wax.

6. A method of producing lubricating oil of high viscosity index and low pour point comprising extracting the oil in accordance with claim 2, adding to the rafiinate so obtained before recovery of solvent therefrom, further amounts of tetrabromoethane and an auxiliary solvent of the class of benzol and its homologues in such proportion as not to produce a separation into two liquid layers at the dewaxing temperature, cooling the mixture to below the desired pour point whereby the wax precipitates out, removing the wax from the oil-solvent solution and recovering the solvents from the dewaxed oil solution and from the wax.

'l. A method of producing a lubricating oil of covering the solvents therefrom.

8. Themethod of processing wax produced by the method of claim 5 comprising dissolving said high viscosity index and low pour point compris wax in a mixture containing tetrabromoethane quantity of a mixture of tetrabromoethane and' benzol and its homologues.

- ERNST TERRES. JOSEF MOOS.

\ ERICH SA'EGmBARlTI-I. 

